Stator blade construction for turbomachines

ABSTRACT

THERE IS DISCLOSED A STATOR BLADE CONSTRUCTION FOR TURBOMACHINES (E.G. TURBINES, OR PUMPS OR COMPRESSORS) IN WHICH THE POSITION OF THE STATOR BLADES OF EACH STAGE IS DEFINED AXIALLY AND READIALLY IN AN ANNULAR HOUSING BY MEANS OF COAXIAL PLANE ANNULAR, CYLINDRICAL, OR CONICAL SURFACES FORMED IN THAT HOUSING BY TURNING OR BORING OPERATIONS.

H808 7 XR 5 5611 884 BEST AVAILABLE COPY Feb. 9, 1971 F. ZERLAUTH 3,561,884

STATOR BLADE CONSTRUCTION FOR TURBOMACHINES Filed Oct. l1. 1968 Inventor: Ferdinand Zerlouth BY l l MJ 0.402..

AT ORNEYS United States Patent O U.S. Cl. 415-218 1 Claim ABSTRACT F THE DISCLOSURE There is disclosed a stator blade construction for turbomachines (eg. turbines, or pumps or compressors) in which the position of the stator blades of each stage is defined axially and radially in an annular housing by means of coaxial plane annular, cylindrical, or conical surfaces formed in that housing by turning or boring operations.

The present invention pertains to turbomachines and, more particularly, to the fastening of the stator blades of such machines into the housing thereof. Theterm turbomachine is intended to denote a turbine-type machine whether for development of mechanical energy at a rotating shaft from a uid owing through the machine as in a turbine, or for the delivery of energy from a rotating shaft to the fluid, as in a pump or compressor. The invention provides a blade fastening in which at least some of the grooves in the housing for receipt of the roots or feet of the stator blades or stator blade segments are open. Further, these open grooves include at least one radially acting cylindrical positioning or indexing surface and at least one axially acting plane annular positioning surface. In addition, these grooves include, in the vicinity of these annular positioning surfaces, a radially acting holding groove. Moreover, in the blade fastening of the invention the feet of the stator blade or stator blade segments possess a complementary radially acting cylindrical positioning surface and a complementary axially acting plane positioning surface. They also include a radially acting holding member which fits into the holding groove of the stator blade housing or blade carrier, and an axially acting lock for the blades or blade segments. The term radially acting positioning surface or radial positioning surface is used herein to denote a surface which establishes the radial position of the member on which it is formed, or of another member which is brought to bear against that surface, and the term axially acting positioning surface" or axial positioning surface is similarly defined in respect of axial positions.

A fastening of the stator blades in accordance with the invention has the advantage that the fabrication of the housing is much simplified. It is sufficient, to make up the step-shaped inner surface of the housing, to apply axial and radial motions to turning and boring tools. Drilling operations are reduced to a minimum. The result is a substantial reduction in manufacturing time and in the jigs and fixtures required, and also an improvement in the accuracy of the dimensions achieved. The blades or blade segments can, moreover, be set in more easily and more accurately.

In the vicinity of the cylindrical positioning surface of the guide blade groove, there can be provided an axially acting closed groove into which a locking device is to be inserted. In this way, the locking device will extend over the heads of the blades so that it may additionallyand simultaneously operate to guide the fiow of the working substance through the conduits of the rotor blades,

BEST AVAILABLE copy ice and eventually also serve to protect the rotor blade support against excessive temperatures.

The cylindrical positioning surface of the open stator blade groove can simultaneously serve as the exterior positioning surface of the axial abutment groove and as an inner positioning surface for the bearing edge of the locking groove. In this way, three positioning surfaces can be produced in a single machining operation.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be further described in terms of an exemplary, non-limitative embodiment and with reference to the accompanying drawing in which the single figure of drawing is a fragmentary axial section through the stator of a turbomachine in accordance with the invention. In the drawing, the stator blades of two adjacent stages of the machine illustrate two embodiments of the stator blade construction of the invention.

DESCRIPTION OF PREFERRED EMBODIMENT In the drawing, and referring first to the stator blading of the left-hand generally indicated at 31, the stator housing 25 includes an open groove 1 for the roots or feet 2 of the stator blades or stator blade segments 3. This groove is formed by machining. The radial positioning surface 4 of the groove 1 is cylindrical in shape and is produced by a purely axial motion of a cutting or boring tool. The surface 4 of each stage may be in two parts, the two parts being separated by a deepened portion of the groove 1. The axial positioning surface 5 in contract is the result of radial motion of the cutting tool only. The same is true of the correspondingly numbered elements of structure associated with the right-hand stage 32. It can be seen that in this way there is produced on the interior of the stator housing a step-shaped surface, producing radially and axially open grooves at the successive radial and axial ring-shaped surfaces thereof. These grooves serve to support the stator blades or blade segments, which are inserted from the large diameter end of the housing.

To hold the stator blades or blade segments of each stage there is provided adjacent the positioning surface 5 a radially operative holding groove 6, cut below the surface 5. The holding groove 6 can be produced in one machining operation together with the cylindrical positioning surfaces 4. The diameter of the outer positioning surface of the groove 6 (identified at 11 in the right-hand stage 32) then has the same value as the diameter of the positioning surface 4 of the open groove 1.

For each stage, a locking groove 12 is cut into the cylindrical positioning surface 4, at or near the axial end of that surface 4 which is adjacent the large-diameter end of the housing. The groove 12 serves to receive stator blade locking segments l0, which are seen to be located axially of the machine opposite the ring of rotor blades on the large-end side of the stator blades held in position by those locking segments. The Shape of the groove 12 is chosen so that it can be cut primarily by radial motion of the cutting tool. In this process, accurate dimensioning need be held only for the positioning surface 14, which must be at a specified distance from the axial positioning surface 5 to the left thereof in the figure. By a subsequent axial motion of a cutting tool there is produced the abutment edge or lip 17 whose outside diameter, defining the positioning surface 15, must be carefully worked to a specified dimension. The positioning surface 16 on the inside diameter of the abutment edge 17 has the same diameter as the positioning surface 4, in each stagev the tool need only be moved axially toward the small diameter and of the housing once it has reached the radially outer limit desired for groove 12.

The method described for machining the interior surface of the stator has the advantage that the positioning surfaces necessary to locate the stator blades in the stator blade carrier or housing can be produced with a minimum of profile cutting tools. Instead, it sufces to employ normal cutting or grinding tools, moved axially or radially, in order to form the cylindrical and plane positioning surfaces.

The feet 2 of the stator blades or blade segments 3 can be set into place by simple axial motion into the ready-prepared grooves 1. The locking segments 10, on the other hand, are inserted radially circumferentially into their locking grooves 12. The radially operative holding edge or fillet 9 on the blade feet is fitted at its positioning surface 7 on the positioning surface 4 of the housing. As is evident from the drawing, part of the positioning surfaces may be relieved by radial motion of the cutting tool. In this way, there is achieved the advantage of ready installation of the blades without requiring adherence to close tolerances. The holding ridge 9 is further located by engagement of its surface 22 on the support surface 23 of the groove 6. As to its axial location, the blade root is supported at one axial end thereof by engagement of its surface 8 on the annular housing surface 5. At the other axial end, the surface 19 of the locking member 10 bears against the positioning surface 18 of the blade foot 2. In this way, the stator blades are tightly fastened into the housing. The result is that their weight, the stresses exerted thereon by the working substance passing through the machine` vibrational stresses. and also those due to distortion of the blades and of the locking members on temperature changes, are borne by positive interengagement of elements requiring rupture before failure, and not merely by forces of friction.

In addition, the blade ring, and more particularly the feet 2 of the blade segments, can be provided with a cylindrical locating surface 20 on the axial side thereof away from the ridge 9, to bear against a complementary cylindrical locating surface 21 of the locking segments 10.

For less highly stressed blades it may be sufficient if the blade feet are held against radial motion only at one axial end thereof, as indicated at 9 for the stage 32 at the right in the drawing, the other axial end of the blade feet being positioned only with axially holding surfaces 18 and 19 on the blade feet and locking members. That is, in stage 32, the members 2 and 10 do not include the radially acting surfaces 20 and 21 which appear on those members in stage 31.

The locking segments 10 are positioned against radial motions at the surfaces and 16 of the abutment edge 17. In respect of axial stresses, the segments 10 bear in each of stages 31 and 32 at the surface 13 thereof on the surface 14 of the groove 12. The result is that the locking segments are in condition to support at their surfaces 19 axial stresses delivered to them at the surface 18 of the blade feet. They can also support at their surfaces 21, when provided, a portion of the radial stresses which are exerted from the blade root via the surface 20.

There is thus achieved by the simplest means a fastening of the stator blades which makes it possible even with open grooves to hold the blades dependably against stresses in any direction and to withstand all of the stresses to which the blades may be exposed including those imposed by the working substance and also by vibration.

The blades may be provided with individual feet. The feet 2 illustrated may, however, extend over a substantial sector uniting a plurality of blades into a single segment. The invention s of particular advantage when the blades are so collected into segments because the feet thereof are readily inserted and held actually into the grooves therefor.

The invention thus provides a stator blade assembly for turbomachines comprising an annular housing having CII BEST AVAILABLE COPY formed on the inner wall thereof at least one groove 1 for the stator blades of each stage of the machine. This groove includes as bounding surfaces thereof a radially extending annular surface of revolution 5. an inwardly facing axially extending surface of revolution 4, and an outwardly facing axially extending surface of revolution 23. This outwardly facing axially extending surface 23 defines a radially operative, axially facing groove 6. The assembly further includes a plurality of stator blade feet 2 having formed thereon surfaces 8 and 7 respectively complementary to and engageable against said radially extending and inwardly facing axially extending surfaces 5 and 4. The feet include an axially extending annular ridge 9 adapted to t in the axially facing groove 6. The assembly further includes locking means comprising a plurality of locking members 10 adapted to hold those feet against the radially extending surface 5 of the housing.

Preferably the housing of the assembly has formed therein for each stage a second groove l2 bounded in part by a radially extending surface 14 facing the radially extending surface 5, and the locking means and blade feet are engaged together between the facing radially extending surfaces 5 and 14. Desirably, the axially facing groove 6 is bounded at the radially outer limit thereof by the inwardly facing axially extending surface 4. The second groove 12 includes an axially extending undercut portion defining an axially extending housing ridge 17 bounded on the radially inner side by the inwardly facing axially extending surface 4 of its stage. Preferably. the locking means comprise a plurality of sectors 10 insertable into the second groove l2. The sectors are positioned radially by at least one side of the axially extending housing ridge 17. The locking means and blade feet engage each other at radially extending surfaces 18 and 19, and may further engage each other at axially extending surfaces 20 and 21.

In each of one or more stages of the stator blade assembly of the invention (or in the single stage thereof, in single-stage turbomachines embodying the invention), provision may be made for the introduction of a heating or cooling medium. To this end one or more bores 35 may be provided through the wall of the housing 25, opening into the locking groove 12 of the selected stage or stages, and additional bores 34 may then be provided through the blade locking segments 10. A heating or cooling medium such as a cooling gas. for example, introduced through the bores 35, will then ow into the annular space 33 and thence through the throat 36 connecting it to the interior of the housing and over the feet of the adjacent stator blades 32. Introduction of a cooling gas in this way makes possible a substantial reduction in temperature at the blade feet, so that they need not be made of the same high-temperature resistant material as the blades themselves.

In the description of the invention hereinabove made and in the appended claims, repeated reference has been made to a housing. This is the housing of the stator blades. That is, it is the stator blade carrier. It is not necessarily the same thing as the housing of the turbomachine.

While the invention has been described hereinabove in terms of a number of preferred embodiments, the invention itself is not limited thereto; rather, the invention comprehends all modifications of and departures from those embodiments properly falling within the spirit and scope of the appended claim.

I claim:

1. A stator blade assembly for multi-stage axial ow turbomachines comprising an annular housing having a high-pressure end and a low-pressure end, said housing having:

(a) a first groove for reception of the stator blade roots of that stage;

(bl said groove being open toward the low-pressure end of the housing;

(c) said groove being bounded at least in part by an BEST AVAILABLE COPY inside cylindrical surface, by a first plane annular surface facing the low-pressure end of the housing, said first plane annular surface being of smaller diameter than said cylindrical surface, and by a rc taining groove cut below said annular surface; said housing further having formed on the inner wall thereof for each stage:

(d) a second groove on the low-pressure side of said first groove and of larger diameter than said rst groove, said second groove being bounded in part by a second plane annular surface facing the highpressure end of the housing and of larger diameter than said cylindrical surface;

said assembly further comprising for each stage:

(e) a plurality of stator blade roots having formed thereon an outer cylindrical surface mating with said inside cylindrical surface, an axial extension engageable in said retaining groove, and a plane annular References Cited UNITED STATES PATENTS 2,763,462 9/1956 McDowall et al. 253--69 2,980,396 4/l961 Movsesian 253-78 2,982,519 5/1961 Haworth etal 253-78 2,295,751 1/1967 Sceggel 230-133 15 HENRY F. RADUAZO, Primary Examiner U.S. Cl. X.R. 415-79 

